Video: Lysosomes

Brief Summary

Lysosomes are membrane-enclosed organelles responsible for degrading macromolecules and biological polymers through hydrolytic enzymes in an acidic environment. They originate from the Golgi apparatus and exist in various forms, including primary and secondary lysosomes, each participating in different membrane traffic pathways like phagocytosis, endocytosis, and autophagy. Secretory lysosomes, found in cells like macrophages and melanocytes, perform both degradation and secretion of proteins and cytokines, contributing to processes like pigmentation and immune response. Plant cells have similar vacuoles that, in addition to degradation, store nutrients and regulate turgor pressure.

• Lysosomes degrade macromolecules and biological polymers.
• They contain hydrolytic enzymes active in an acidic environment.
• They participate in phagocytosis, endocytosis, and autophagy.
• Secretory lysosomes secrete proteins and cytokines.
• Plant cells have vacuoles with similar functions, including nutrient storage and turgor pressure regulation.

Lysosomes

Lysosomes are spherical sacs enclosed by membranes, originating from the Golgi apparatus. Their primary function is to break down macromolecules and biological polymers, which are released during membrane trafficking events like secretion, endocytosis, autophagy, and phagocytosis. This degradation process is facilitated by hydrolytic enzymes that operate in the acidic environment within the lysosome. These acid hydrolases are crucial for cellular processes, including cell signaling, energy metabolism, plasma membrane restoration, and managing discharged materials.

Primary and Secondary Lysosomes

Newly formed lysosomes, known as primary lysosomes, originate from the inner Golgi sacs and are dynamic, capable of dividing or fusing with macromolecules, other organelles, and the plasma membrane. When primary lysosomes fuse with substances destined for degradation, they transform into secondary lysosomes. These secondary lysosomes participate in various pathways, becoming phagosomes, endo-lysosomes, digestive vacuoles, and autophagosomes. While there isn't a strict distinction between these forms, they are defined by their involvement in different membrane traffic pathways, representing morphologically diverse organelles with the common function of degrading intracellular material.

Secretory Lysosomes and Plant Cell Vacuoles

Secretory lysosomes are specialized lysosomes that combine features of both conventional lysosomes and secretory granules. They are abundant in cells such as macrophages, hematopoietic cells, and melanocytes. In addition to lysosomal enzymes, secretory lysosomes secrete antimicrobial proteins and cytokines, playing a role in pigmentation, coagulation, wound repair, and immunological functions. Plant cells contain vacuoles filled with hydrolytic enzymes similar to lysosomes but with diverse functions. These vacuoles not only degrade substances but also store nutrients and waste products and regulate turgor pressure.